Air is being compressed in a cylinder with a volume of 0.025 m^3 under a constant pressure of 3.0*10^5 Pa and the volume of the air in the cylinder is reduced to 0.020 m^3.

a. By how much is the volume of the air reduced?
b. How much work is done in the process?
c. The cylinder is thermally insulated, making the process adaibatic. What is the change in the internal energy of the gas?

I don't know what to do at all! I read my whole textbook about 10 times and can't find anything like this.

a) Subtract the final volume from the initial volume. That is the reduction in volume. Call it delta V

b) Work = P * (delta V)

c) Qin - Wout = change in internal energy (delta U) is a statement of conservation of energy for the gas. Qin is the heat transfered in, which is zero in this case. Wout is the work done BY the gas, which is -W. Use W from part (b)